3-Phenyluracils of the formula I and the corresponding thio- and dithiouracils are known in principle from WO 01/83459. They are prepared in accordance with the teaching given in WO 01/83459 by the following processes A to C. In the following schemes A to C, the variables Ar and A are each as defined above, Hal is halogen and Q is an optionally substituted uracil, thiouracil or dithiouracil radical:    (A) condensation of a substituted benzoic acid with a substituted sulfuric diamide in the presence of N,N-carbonyldiimidazole (CDI) or conversion of the carboxylic acid to its acid chloride and subsequent reaction of the acid chloride with the sulfuric diamide in accordance with the following scheme A:

A disadvantage of this procedure is that the benzoic acid used is only obtainable from the precursor ester by cleavage using boron tribromide with corresponding salt formation. In addition, the yield of the condensation with sulfonic diamides is only between 16 and 45%. The detour via an acid chloride prepared beforehand also leads in only 26% yields to the desired benzoylsulfuric diamide, which additionally has to be freed of its impurities by chromatography.    (B) Replacement of a halogen atom by a uracil, thiouracil or dithiouracil radical by the following scheme B:

The process B has the disadvantage that the haloaromatic used first has to be prepared in a complicated manner by a Sandmeyer reaction. In addition, the selectivity of the reaction with respect to the halogen radical is unsatisfactory when further halogen substituents are present on Ar.    (C) Reaction of an aniline compound with an oxazinone and subsequent alkylation of the resulting 3-phenyluracil in the presence of a base according to the following scheme C:

In this scheme, the variable R1is as defined above.
It is disadvantageous that the oxazinone used first has to be prepared in a costly and inconvenient manner by reacting an aminocrotonic ester with a dialkylcarbamoyl chloride and subsequently cyclizing with phosphorus oxychloride, phosphorus pentachloride or oxalyl chloride. This process is likewise not sufficiently economically viable as a consequence of the starting materials used and the reaction stages.
It is known that 3-phenyluracils can be prepared by reacting phenyl isocyanates with aminoalkenecarboxylic esters; see, for example, EP 0 831 091. However, the phenyl isocyanates used in EP 0 831 091 do not have an acylsulfonamide group.
Moreover, it is known that iso(thio)cyanate groups may enter into a multitude of different reactions with sulfonamide groups. For instance, iso(thio)cyanante groups may react with sulfonamide groups which bear a hydrogen atom on the nitrogen atom to form sulfonylureas. For example, J. Cervello and T. Sastre in Synthesis 1990, 221-222, describe the reaction of tolylsulfonamides with aryl isocyanantes to form the corresponding N-tosylurea.
U.S. Pat. No. 4,309,209 discloses that phenyl isocyanates react with chloromethane(N-methyl)-sulfonamide (═ClCH2SO2NHCH3) to form a 1,2,4-thiadiazolidine-1,1,3-trione.
P. Schwenkkraus and H.-H. Otto in Arch. Pharm. (Weinheim) 326, 437-441 (1993) describe the reaction of 3-haloalkyl-β-sultams, i.e. cyclic sulfonamides, with phenyl isocyanate to form carbamoyl compounds.
DE 3433391 discloses the reaction of the cyclic sulfonamide saccharin with acyl isocyanates to give N-acylated saccharin derivatives.
B. A. Arbuzov, N. N. Zobova and N. R. Fedotava in JZV Akad Nauk SSSR, Ser Khim 1990, 2874 (engl. translation: Bulletin of the Academy of Sciences of the USSR, Division of Chemical Sciences, vol. 39, (1990) p. 2610) describe the N- and O-acylation of saccharin by reacting with a trifluoroacetyl isocyanate.